Process of producing nonwoven fabrics using aziridine-modified polyurethane bonding agent

ABSTRACT

NON-WOVEN FABRICS WHICH COMBINE GOOD TENSILE STRENGTH WITH POROSITY, AIR-PERMEABILITY, FLEXIBILITY, SOFTNESS, AND THE APPEARANCE AND HANDLE OF A WOVEN FABRIC. PRODUCTS OF THE INVENTION, ALTHOUGH MADE FROM WOOL, DO NOT SHRINK WHEN WASHED IN AQUEOUS SOAP OR DETERGENT FORMULATIONS. EXAMPLE: AN AZIRIDINE-MODIFIED POLYURETHANE IS DEPOSITED ON WOOL FIBERS WHICH ARE THEN ARRANGED IN THE FORM OF A THIN WEB AND CURED AT A TEMPERATURE OF ABOUR 100-170* C. UNDER A PRESSURE OF ABOUT 1000-5000 P.S.I.

PROCESS OF PRODUCING NONWOVEN FABRICS USING AZIRIDINE-MODIFIEDPOLYURETHANE BONDING AGENT Howard L. Needles, Davis, and William L.Wasley, Berke- ":eley, Califz, assignorsto the United States of Americaas represented by-the Secretary-of Agriculture 3 No Drawing. FiledNov.19, 1969, Ser. No. 882,407

. v I Int. Cl. D04h 1/00 U.S. Cl. 264-123 5 Claims ABSTRACT OF THEDISCLOSURE :Non-woven fabrics which combine good tensile strength withporosity, air-permeability, flexibility, softness, and the appearanceand handle of a woven fabric. Products of the invention, although madefrom wool, do not shrink whenwashed in aqueous soap or detergentformulations. 'Example: An aziridine-modified polyurethane is depositedon wool fibers whichare then arranged in the form of a thin web andcured at a temperature of about 100170 C.-under a pressure of about1000-5000 p.s.i.

[or knitting. More particularly, the invention concerns the provisionbfnon-wovenfabrics which exhibit many of the characteristics of typicalwoven fabrics. Thus, the products of the invention combine good tensilestrength with porosity, air-permeability, flexibility, softness, and

the appearance and handle of a woven fabric. Moreover, although.theproducts of the invention are made from wool, they 'do, not shrinkwhen 'washed in aqueous soap or jde tergent formulations. Furtherobjects and advantages of thelinvention will be evident from thefollowing description wherein parts and percentages are by weight unlessotherwise. specified.

Certainnon-woven fabrics are now available in commerce. These productsconsist of a skeleton of textile fibers bonded together by such resinousmaterials as polyvinyl esters,. polyacrylates, polystyrene,polyvinylidenes, and copolymers of these substances and the like. Acommon property of these known products is that they are stiff. Indeed,they are used as stiffening materials for 'lapels, collars, and similargarment parts. Another disadvantage of the known non-woven fabrics isthat they cannot withstand the stresses encountered in laundering. Whensubjected to the, usual agitation in soap (or detergent) .and hotwaterformulations they are ruptured or even disintegrated. For example,Nottebohm (U.S. Pat.

2,719,803.) explains that non-woven fabrics cannot be washed withoutdamage, and to remedy thisproblem he finds it necessary to protect aninner layer of non-woven fabric by laminating it with outer layers ofconventional woven fabrics.

A primary object of the invention is the provision of novel productswhich avoid the problems outlined above, that is, the provision ofproducts which, among other advantages, are free from stiffness andwhich are stable to washing in aqueous media. I

In accordance with the invention, wool fibers are first Unit d S atPatented Eeb. 15, 1972 coated with an aziridine bonding agent (ashereinafter described). A preferred technique involves dissolving theaziridine in an inert, volatile solvent and applying the resultingsolution to the wool fibers. Typical of the solvents which may be usedare benzene, toluene, xylene, dioxane, diisopropyl ether, dibutyl ether,butyl acetate, chlorinated hydrocarbons such as chloroform, carbontetrachloride, ethylene dichloride, trichloroethylene,1,3-dichlorobenzene, fluorohydrocarbons such as benzotrifiuoride,1,3-bis-(trifluoromethyl) benzene, etc., petroleum distillates such aspetroleum naphthas, etc. Usually it is preferred to use the aziridinesin the form of aqueous emulsions. These can be prepared by customarytechniquesagitation of the aziridine with water and a conventionalemulsifying agent such as an alkylphenoxypoly-(ethyleneoxy) ethanol,polyoxyethylene sorbitan monopalmitate, polyoxyethylene lauryl ether,polyoxyethylene lauryl ether, polyoxyethylene-polyoxypropylene stearate,sorbitan monopalmitate, sorbitan monolaurate, and the like. Theconcentration of the aziridine in the dispersionthis last term beingherein employed in a generic sense to include solutions and emulsions-isnot critical and may be varied depending on such circumstances as thesolubility characteristics of aziridine, the amount of aziridine to bedeposited on the fibers, the viscosity of the dispersion, etc. Ingeneral, a practical range of concentration would be from about 1% toabout 25%. The dispersion may be distributed on the textile material byany of the usual methods, for example, by spraying, brushing, padding,dipping, etc. A preferred technique involves immersing the fibers in thedispersion and then passing them through squeeze rolls to remove theexcess of liquid. Such techniques as blowing air through the treatedtextile may be employed to reduce the amount of liquid which exists ininterstices between fibrous elements. In any case, the conditions ofapplication are so adjusted that the textile material contains theproportion of aziridine desired. Generally, the amount of aziridine isabout from 5 to 25%, based on the weight of the wool fibers but it isobvious that higher proportions may be used for special purposes.

After application of the aziridine, the treated fibers are dried toremove the solvent or dispersing vehicle. The drying may be at roomtemperature, or somewhat elevated temperatures, for example, up to about60 C. The fibers are then arranged to form a thin sheet or web. Thefibers may be arranged parallel, in a criss-cross pattern, or randomly.For best results the fibers are arranged in superposed layers with thefibers of each layer at an angle to the fibers of adjacent layers, thusto provide a multiplicity of points of contact between individualfibers.

The web or sheet of aziridine-treated fibers is then subjected to atemperature of about -l70 C. while under a pressure of about 1000-5000p.s.i. applied, for

example, by heated platens or the like. By this heating aresult is, ofcourse, advantageous as it yields a' product which is like a fabric(i.e, porous, resilient, etc.) and not impermeable and limp like aplastic foil or sheet. Anotherimportant result of the curing step isthat the aziridine is chemically bonded to the wool fibers. Although themechanism of this bonding has not been identified, it is believed toinvolve chemical combination of the aziridine with active radicals inthe wool molecules, these active radicals including carboxyl, hydroxyl,amino, and thiol groups. This chemical combination of the aziridine withthe wool fibers is of advantage as it adds to the durability of theproducts, particularly their ability to be washed without shrinking orother damage.

The non-woven fabrics prepared by the technique described above havemany advantages properties. They are porous, air-permeable, soft,flexible, and resilient. Thus, unlike prior art products they exhibitmost of the properties of the wool fibers themselves so that they areeminently suitable for preparing all kinds of garments. A particularlyimportant advantage of our products is that they can be washed with theusual soap (or detergent) and hot water formulations without rupture,indeed without even shrinking. Moreover, the products display anexcellent resistance to wrinkling and creasing.

The aziridines used in accordance with the invention are those describedand claimed in the co-pending application of Allen G, Pittman andWilliam L. Wasley, Ser. No. 675,038, filed Oct. 13, 1967, now Pat.3,542,505. They may be aptly described as aziridine-modifiedpolyurethanes, and have the structure A is the residue of a polyetherpolyol or polyester polyol having a valence of n,

R is a hydrocarbon radical containing at least two carbon atoms,

R is hydrogen, halogen, lower alkoxy, or a radical of the structure on Rwherein:

CHR"

R" is hydrogen or a lower alkyl radical, n is an integer from 2 to 10,and x is an integer from 1 to 2.

-(In the formulas, 111 represents the number of tetramethylene repeatingunits. This may range, for example, about from 5 to 50.)

The reaction is carried out at about 10 to 40 C., and under essentiallyanhydrous conditions to avoid hydrolysis of the isocyanate groups. Thealkylene imine is supplied in excess to ensure conversion of allisocyanate groups to aziridine groups. it is evident from the formulasabove that modification in the aziridine rings can be effected byselection of the alkylene imine reactant. For example, if propyleneimine is used instead of ethylene imine, the aziridine rings will be ofthe structure In other words, in this case R (in Formula I) is methyl.

Referring to Formula I, above, it is evident that selection of thepolymer intermediatethe polyether or polyester polyurethane containingfree isocyanate groups will determine the values of A, R, R, n, and x.The preparation of these intermediates is Well known in the art; theyare widely used in the production of urethane foams for padding andinsulation applications, and in the production of elastomers. Althoughthe preparation of these intermediates forms no part of the presentinvention, this subject will be explained below to illustrate the widerange of intermediates which may be employed in producing the aziridinederivatives of the invention. Thus, for the purposes of the invention,the intermediate may be any polyether or polyester polyurethane whichcontains at least two free NCO groups per polymer molecule. Preferredare the polymer intermediates having a molecular weight of at least 500,more preferably those having a molecular weight of at least 1000. Also,it is generally preferred to use the polyether-based polymers, forexample, the NCO-containing polyurethanes derived from polyalkyleneether glycols such as polyethylene ether glycols, polytrimethylene etherglycols, polytetramethyleue ether glycols, polypropyleneether glycols,and the like.

THE POLYMER INTERMEDIATES =Polyether (or polyester) polyurethanescontaining free isocyanate groups useful as intermediates for thepresent invention may be prepared, as Well known in the art, by reactinga polyether (or polyester) polyol with a polyisocyanate, using an excessof the latter to ensure provision of free isocyanate groups in theproduct. A typical, but by no means limiting, example is illustrated:

Isoeyanate-terminatcd polyether polyurethane Isocyanate-terminatedpolyether polyurethane (In the above formulas, m represents the numberof tetramethyleneether repeating units. This may range, for example,about from to 50.) v j Representative examples of polyisocyanates whichmay be employed for reaction with the polyether (or polyester) polyol'include: Y L

=toluene;2,4-diisocyanatetoluene-2,G-diisocyanate commercial mixtures of toluene-2,4 and 2,6-diisocyanates ethylene diisocyanate ethylidenediiso'cyan-ate propylene-1,2-diisocyanate cyclohexylene-1,2-diisocyanatecyclohexylene-1,4-diisocyanate 3 m-phenylene diisocyanate-3,3-diphenyl}4;4' biphenylene dii socyanate 44'-biphenylene'diisocyanate 3,3 -'dichlor0-4,'4=biphenylene 'diisocyanate1,6-hexamethylenediisocyanate 1',4 tetrarnethylene-diisocyanate'"1,10-deCamethylenediisocyanate 1,5-naphthalenediisocyanatecu'rherie-ZA-diisbcyanate l-rnethoxy-lfi-phenylenediisocyanate4chloro-1,3-phenylenediisocyanate 4-bromo-1,3-phenylenediisocyanate 4-etho xy-l,3-phenylenediisocyanate 2,4 diisocyanatodiphenylether5,6-dimethyl-1,3-phenylenediisocyanate2,4'-dimethyl-1,3-phenylenediisocyanate 4,4'-diisocyanatodiphenyletherbenzidinediisocyanate 4y6-dimethyl-1,3ephenylenediisocyanate 9,IO-anthracenediisocyanate v I "4,4"-diisbyanatodibenzyl3,3-dimethyl-4,4'-diisocyanatodiphenylmethane2,6-dimethyL'4,4-diisocyanatodiphenyl 2,4-diisocyanatostilbene 3,3'dimethyl-4,4'-diisocyanatodiphenyl3,3'-dimethoxy-4,4'-diisocyanatodiphenyl 1,4-anthracenediisocyanate2,5-fluorenediisocy-anate r1,8-naphthalenediisocyanate2,6-diisocyanatobenzfuran 2,4,6-toluenetriisocyanate, and

p,p',p"-triphenylmethane triisocyanate.

Itis evident that the selection of the polyisocyanate rewant willdetermine the values of R and R in Formula I. For example, where thereactant is a hydrocarbon diisocyanate, R will be a hydrocarbon radicaland R will represent ahydrogenatom forming part of said hydro- .carbonradical. Where the reactant contains a substituent such as "chlorine ormethoxy-as would be the case with, for example, '4-chloro-l,3-phenylenediisocyanate or L methoxy-1,3-phenylenediisocyanate-R will be thebydrocarbon residue of the reactant and R will be thesubstituentchlorine or methoxy in the given examples.

The polymer intermediates useful for the purposes of the invention may,in turn, be derived from any of a wide variety of polyether polyols andpolyester polyols, and representative examples of these polyols aredescribed below:

Among the polyether polyols which may be so used are those prepared byreaction of an alkylene oxide with an initiator containing activehydrogen groups, a typical example of the initiator being a polyhydricalcohol such as ethylene glycol. The reaction is usually carried out inthe presence of either an acidic or basic catalyst. Examples of alkyleneoxides which may be employed in the synthesis include ethylene oxide,propylene oxide, any of the isomeric butylene oxides, and mixtures oftwo or more different alkylene oxides such as mixtures of ethylene andpropylene oxides. The resulting polymers contain a polyether backboneand are terminated by hydroxyl groups. The number of hydroxyl groups perpolymer molecule is determined by the functionality of the activehydrogen initiator. For example, a difunctional alcohol such as ethyleneglycol (as the active hydrogen initiator) leads to polyether chains inwhich there are two hydroxyl groups per polymer molecule. Whenpolymerization of the oxide is carried out in the presence of glycerol,a trifunctional alcohol, the resulting polyether molecules contain anaverage of three hydroxyl groups per molecule. Even higherfunctionalitymore hydroxyl groupsis obtained when the oxide ispolymerized in the presence of such polyols as pentaerythritol,sorbitol, dipentaerythritol, and the like. In addition to those listedabove, other examples of polyhydric alcohols which may be reacted withalkylene oxides to produce useful polyether polyols include:

propylene glycol trimethylene glycol 1,2-butylene glycol 1,3-butanediol1,4-butanediol 1,5-pentanediol 1,2-hexylene glycol 1,10-decanediol1,2-cyclohexanediol 2-butene-1,4-dio1 3-cyclohexene-1,2-dimethanol4-methyl-3-cyclohexene 1,1-dimethano1 3-methylene-1,5-pentanedioldiethylene glycol (Z-hydroxyethoxy)-1-propanol 4- (Z-hydroxyethoxy-1-butanol 5-(Z-hydroxypropoxy)-1-pentanol1-(Z-hydroxymethoxy)-2-hexanol l-(l-hydroxypropoxy)-2-octanol3-allyloxy-1,5-pentanediol 7 2-allyloxymethyl-Z-methyl-1,3-propanediol[(4-pentyloxy) rnethyl]-1,3-propanediol3-(o-propenylphenoxy)-1,2-propanediol thiodiglycol 2,2' [thiobis(ethyleneoxy) ]diethanol polyethyleneether glycol (molecular weightabout 200) 2,2'-isopropylidenebis(p-phenyleneoxy)diethanol1,2,6-hexanetriol 1,1,l-trimethylolpropane3-(2-hydroxyethoxy)-1,2-propanediol 3- (Z-hydroxypropoxy 1,2-propanediol 2,4-dimethyl-2- (Z-hydroxyethoxy) methylpentanediol- 1,51, l,1-tris[ (Z-hydroxyethoxy methyl] ethane 1, l 1 -tris(Z-hydroxypropoxy methyl] propane triethanolamine triisopropanolamineresorcinol pyrogalol phloroglucinol hydroquinone 4,6-di-tertiarybutylcatechol catechol orcinol methylphloroglucinol hexylresorcinol3-hydroxy-2-naphthol 2-hydroxy-l-naphthol 2,5-dihydroxy-1-naphtholbis-phenols such as 2,2-bis-(p-hydroxyphenyDpropan andbis-(p-hydroxyphenyl methane 1,1,2-tris- (hydroxyphenyl ethane1,1,3-tris- (hydroxyphenyl) propane.

An especially useful category of polyether polyols are thepolytetramethylene glycols. They are prepared by the ring-openingpolymerization of tetrahydrofuran, and contain the repeating unit in thepolymer backbone. Termination of the polymer chains is by hydroxylgroups.

The polyester polyols which may be employed as precursors for theaziridines of the invention, are most readily prepared by condensationpolymerization of a polyol with a polybasic acid. The polyol and acidreactants are used in such proportion that essentially all of the acidgroups are esterified and the resulting chain of ester units isterminated by hydroxyl groups. Representative examples of polybasicacids for producing these polymers are oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid, brassylic acid, thapsic acid, maleic acid,fumaric acid, glutaconic acid, a-hydromuconic acid, B-hydromuconic acid,a-butyl-ot-ethylglutaric acid, u,fi-diethylsuccinic acid, o-phthalicacid, isophthalic acid, terephthalic acid, hemimellitic acid,trimellitic acid, trimesic acid, mellophanic acid, prehnitic acid,pyromellitic acid, citric acid, benzenepentacarboxylic acid,1,4-cyclohexanedicarboxylic acid, diglycollic acid, thiodiglycollicacid, dimerized oleic acid, dimerized linoleic acid, and the like.Representative examples of polyols for forming these polymers includesethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol,1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol,butene-l,4-diol, 1,5-pentane diol, 1,4-pentane diol, 1,3-pentane diol,1,6-hexane diol, hexene-1,6-diol, 1,7-

heptane diol, diethylene glycol, glycerine, trimethylol propane,1,3,6-hexanetriol, triethanolamine, pentaerythritol, sorbitol, and anyof the other polyols listed hereinabove in connection with thepreparation of polyether polyols. 5 An interesting class of polyesterpolyols are those which include polyether units so that they may beconsidered as polyester polyols or as polyether polyols, depending onwhether the ester or the ether groups are in majority. The compounds maybe produced by the condensation polymerization of any of theabove-mentioned polybasic carboxylic acids with a polyalkyleneetherglycol-typically, a polyethyleneether glycol having a molecular weightof about 200 to 2000-using the glycol in the required proportion toassure termination by hydroxyl.

Esters of the hydroxyl-containing acid, ricinoleic acid, form anothercategory of useful polyester polyols. Typically, one can use esters ofricinoleic acid with ethylene glycol, propylene glycol, glycerol,pentaerythritol, diglycerol, dipentaerythritol, polyalkyleneetherglycols, and the like. Representative of this category of polyesterpolyols is castor oil which is composed mainly of the tri-glyceride ofricinoleic acid.

The invention is further demonstrated by the following illustrativeexamples.

EXAMPLE 1 The aziridine-modified polyurethane used in this instance wasprepared as described in Ex. 4 below. It has the structure A 10%solution of the aziridine-modified polyurethane in toluene was preparedand used to treat wool sliver (a loose assembly of wool fibers). Thewool sliver was passed through the solution and then excess liquidremoved, using pad rolls to attain an 80-100% wet pick-up of solution.The treated sliver was dried at room temperature. The uptake ofaziridine was 8%.

The dried sliver was cut into 15 cm. long segments (3 grams each) whichwere spread into 15 x 15 cm., singleply or 2-ply (crossed), webs betweensheets of aluminum foil. The web in each foil was pressed at 2000 p.s.i.and 150 C. for 5 minutesin a hydraulic press. After removal from thepress, the foil was removed to yield non-woven fabric samples whichweighed approximately 13 mg./cm. The products were very resilent andcould be laundered. Various tests were conducted on the samples, theresults being tbulated below:

*ASTM test method D-89-49, l-incli wide strip.

EXAMPLE 2 The procedure described in Example 1 was repeated with theexception that the concentration of the aziridine solutions wasincreased to give uptakcs of the aziridine polymer of 14.4% and 28%.Tests were conducted on the resulting products, these including ashrinkproofing test 75 as follows:

Accelerotor shrinkage test This test for shrinkage was conducted in thefollowing way: The samples were milled at 1700 r.p.m. for 2 minutes at40-42 C. in an accelerotor with 0.5% sodium oleatej solution, using aliquor-to-wool ratio of 50 to 1. After this washing operation thesamples were measured to determine their area and the shrinkage wascalculated from the original area. The accelerotor is described in theAmerican Dyestutf Reporter, vol. 45, p. 685, Sept. 10, 1956. Thetwo-minute wash in this device is equal to about 15 home launderings.Conventional woven wool fabrics when treated in this manner exhibit anarea shrinkage of 45 to 50%. The-results obtained are tabulated below:

The procedure described in Example 1 was repeated with these exceptions:The aziridine was that described in Example 6 below. It has thestructure Direction The curing step was at 150 C., 2000 p.s.i. for 10minutes. The products had an 11% uptake of the aziridine polymer. Testson the products are tabulated below:

The following examples illustrate syntheses of the aziridines useful forthe purposes of this invention.

EXAMPLE 4 Preparation of aziridine-modified polytetramethyleneether Ipolyurethane The starting material for this synthesis was a commercialliquid polyurethane having a molecular weight of seem 2000 and anisocyanate '(-NCO) content of 4.1%. It is believed to have the structureCH3 CHa 10 wherein A represents the residue of a polytetramethyleneetherglycol containing about twenty-five -CH CH CH CH -O units.

Two hundred grams (0.1 mole) of the polyurethane were dissolved in 300grams of toluene. While stirring the solution, 8 grams (0.2 mole) ofethylene imine were added dropwise. During the addition, the temperatureof the solution was not allowed to exceed approximately 40 C. At the endof the addition, an infrared spectrum of the solution revealed noresidual NCO groups. This indicated preparation of the desired aziridinederivative.

EXAMPLE 5 The starting material for this synthesis was a commercialliquid polyether polyurethane having a molecular weight of about 850 andan isocyanate (-NCO) content of about 9.5%. It is believed to have thestructure.

wherein A represents the residue of a polytetramethyleneether glycolcontaining about seven -CH -CH CH --CH O units.

One hundred grams (0.12 mole) of the liquid polyurethane was dissolvedin 300 ml. of dry benzene. While stirring, 13 ml. (0.26 mole) ofethylene imine was added at a rate slow enough that the reactiontemperature did not rise above 40 C.

EXAMPLE 6 The starting material for the synthesis was a commercialliquid polyether polyurethane having a molecular weight of about 1300and an isocyanate (-NCO) con- 14 45 tent of 6.5%. It is believed to havethe structure EXAMPLE 7 A polypropyleneether glycol of molecular weightabout 6000' was reacted with toluene diisocyanate in conventional mannerto form an isocyanate-termined polyurethane. This, in turn, was reactedwith propylene imine 12 to form an aziridine-modified polyurethane withterminal R" is hydrogen or a lower alkyl radical, groups of thestructure n is an integer from 2 to 10, and

CH x is an integer from 1 to 2,

3 (b) arranging the treated wool fibers into the form CH2 5 of a thinweb, and

(c) while constraining the fibers in the form of. a thin web, curing theweb at a temperature of about 100- (IE-CH3 170 C. and a pressure ofabout 1000-5000 p.s.i.

l -CONH-P NHOON 2. The process of claim 1 wherein A is the residue of aFifty grams of the aziridine-modified polymerhaving polyalkyleneetherglycol and n is 2.

a molecular weight of 6300-6800 and containing 0.36 to 3, The process oflaim 1 whe i 0.38 milli-equivalents of imine per gram of polymerwasdissolved in 50 grams of benzene and 2 grams of a commercial emulsifier,a polyoxyethylene-polyoxypropylene R5 monostearate, was added. Whilestirring the solution in a is the tolylene radical. blendor, water wasgradually added to make 1000 gram 4. The process of claim 1 wherein theaziridine-modified of an emulsion. polyurethane has the structure (in,CH, CH; 0 0 0 I 0 CH,

It II II I /N NH NH-CO(CH CH CHg-CH -OM-C-NH NH-C-N CH1 Hz Having thusdescribed the invention, what is claimed is: 5. The process of claim 1wherein the aziridine-modified 1. A process for preparing a non-wovenfabric which polyurethane has the structure comprises $H3 CHI Cs: 0 (I)3 IO /CH: l Ni J-NH NH-ll-O(GH -CH CH2-CHg0)25-CNH NH-N\l OH: H]

(a) depositing on wool fibers an aZiridine-modified References Citedpolyurethane Of the structure UNITED STATES PATENTS 0 3,542,505 11/1970Pittman et a1. 8127.6

U AO -NH-RNH N i n ROBERT F. BURNETT, Primary Examiner wherein: R. O.LINKER, JR, Assistant Examiner A is the residue of a polyether polyol orpolyester polyol having a valence of n, R is a hydrocarbon radicalcontaining at least two 156 296, 331; 161-157, 170

carbon atoms, R is hydrogen, halogen, lower alkoxy, or a radical of thestructure

